Many diseases, including those induced by bacterial, viral or environmental exposures, result in prolific neoplastic growth, such as with cancer or leukemia, or in severe immune system degradation, as occurs with acquired immunodeficiency syndrome. Generally, methods for treating these diseases have included surgery, radiation therapy and drug therapy. Among the more effective antineoplastic agents developed are ether lipids, such as 1-O-Octadecyl-2-O-methyl-sn-glycero-3-phosphocholine, and thioether lipids, such as 1-O-Hexadecyl-2-O-methylthioglycero-3-phosphocholine. See, for example, Morris-Natschke et al., J. Med. Chem., 29:2114 (1986); Bosies et al., U.S. Pat. No. 4,444,766, issued Apr. 24, 1984. However, therapeutic treatment with these ether lipid and thioether lipid agents has been noted to result in adverse side effects, for example necrosis of the tail vein and impairment of antibody production in treated mice. See, for example, Kudo et al., Lipids, 2.2:862 (1987) and Andreesen, Prog. biochem. Pharmacol., 22:118 (1988).
Therefore, a need exists for new compounds that are therapeutic in the treatment of neoplastic and immune system diseases and that will not cause significant adverse side effects.